Method and apparatus for dynamically adjusting data transmission parameters and controlling h-arq processes

ABSTRACT

A method and wireless transmit/receive unit (WTRU) for enhanced uplink data transmission is disclosed. A transport block size for transmission of enhanced uplink data is selected. A medium access control (MAC) protocol data unit (PDU) is segmented into a plurality of segments on a condition that the MAC PDU does not fit in a transport block according to the selected transport block size. A transport block is produced having the transport block size and includes at least one of the plurality of segments. The transport block is transmitted over an enhanced uplink channel and an indication of the transport block size is transmitted over an associated physical control channel.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14,291,747, filed May 30, 2014, which is a continuation of U.S. patentapplication Ser. No. 12/539,186, filed Aug. 11, 2009, which issued onJun. 3, 2014 as U.S. Pat. No. 8,743,710, which is a division of U.S.patent application Ser. No. 11/140,034 filed May 27, 2005, which issuedon Sep. 1, 2009 as U.S. Pat. No. 7,584,397, which claims the benefit ofU.S. Provisional Application No. 60/578,728 filed Jun. 10, 2004, all ofwhich are incorporated by reference as if fully set forth.

FIELD OF INVENTION

The present invention is related to a wireless communication systemincluding a wireless transmit/receive unit (WTRU) and a Node-B. Moreparticularly, the present invention is related to a method and apparatusfor dynamically adjusting data transmission parameters such asmodulation and coding scheme (MCS) and transport block set (TBS) size,and assigning and releasing a hybrid-automatic repeat request (H-ARQ)process used to control the transfer of data between the WTRU and theNode-B.

BACKGROUND

In 3rd generation cellular systems, adaptive modulation and coding(AM&C) and H-ARQ schemes are being investigated for incorporation intoan enhanced uplink (EU) operation designed to offer low transmissionlatency, higher throughput, and more efficient use of physicalresources.

The AM&C scheme allows an MCS to be dynamically adjusted on a transmittime interval (TTI) basis whereby, for each TTI, the MCS is selected tomake the most efficient use of radio resources and to provide thehighest possible data rates. A less robust MCS uses less physicalresources, but is more vulnerable to errors. A more robust MCS uses morephysical resources, but offers greater protection against errors.

The H-ARQ scheme is used to generate transmissions and retransmissionswith low latency. A primary aspect of the H-ARQ scheme is that datareceived in failed transmissions can be soft combined with successiveretransmissions to increase the probability of successful reception.Either Chase Combining (CC) or incremental redundancy (IR) may beapplied. When CC is applied, the same MCS is chosen for theretransmission. When IR is applied, a more robust MCS is used in eachretransmission.

SUMMARY

The present invention is implemented in a wireless communication systemincluding a WTRU which transfers data to a Node-B. Data transmissionparameters such as TBS size are dynamically adjusted on a TTI basis.Optionally, MCS may also be adjusted. An H-ARQ process used to controlthe transfer of data between the WTRU and the Node-B is assigned andreleased, as required. The WTRU transmits and retransmits data to theNode-B through an enhanced uplink (EU) dedicated channel (E-DCH) inaccordance with feedback information received from the Node-B. The WTRUqueues data for transmission, and determines a transmission status ofthe data. The transmission status is set by a controller in the WTRU toone of “new transmission,” “successful transmission,” “retransmission”and “restarted transmission.” For each TTI, the WTRU initiates an EUtransmission to the Node-B which identifies either explicitly orimplicitly the retransmission number, new data indication, assignedH-ARQ process, TBS size and optionally MCS.

The transmission status of data is set by the controller in the WTRU to“new transmission” when the data is new data, to “successfultransmission” when an acknowledge (ACK) message is received from theNode-B, to “retransmission” when a non-acknowledge (NACK) message or noresponse is received from the Node-B in response to the transmission ofthe new data, and optionally to “restarted transmission” when aretransmission count exceeds a predetermined maximum number ofretransmissions.

If the transmission status is “new transmission”, an initial H-ARQprocess is assigned. If the transmission status is “retransmission”, thesame H-ARQ process is assigned while incrementing the retransmissioncounter. If the transmission status is “successful transmission”, theH-ARQ process is released. If the transmission status is “restartedtransmission”, which is optional, an H-ARQ process is assigned whileinitializing the retransmission counter and incrementing a new dataindicator (NDI).

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred example, given by way of exampleand to be understood in conjunction with the accompanying drawingwherein:

FIG. 1 is a block diagram of a wireless communication system operatingin accordance with the present invention;

FIG. 2 is a flow diagram of a process for initiating and releasing H-ARQprocesses in accordance with the present invention;

FIG. 3 is a flow diagram of a process including method steps forimplementing CC in accordance with the present invention; and

FIG. 4 is a flow diagram of a process including method steps forimplementing IR in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, the terminology “WTRU” includes but is not limited to a userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, or any other type of device capable of operating in a wirelessenvironment. When referred to hereafter, the terminology “Node-B”includes but is not limited to a base station, a site controller, anaccess point or any other type of interfacing device in a wirelessenvironment.

The features of the present invention may be incorporated into anintegrated circuit (IC) or be configured in a circuit comprising amultitude of interconnecting components.

FIG. 1 is a block diagram of a wireless communication system 100operating in accordance with the present invention. The system 100comprises a WTRU 102, a Node-B 104, and a radio network controller (RNC)106. The WTRU 102 transmits data through an E-DCH 108 with a transmitter120 and receives feedback with a receiver 122 from the Node-B 104through a downlink (DL) signaling channel 110 based on an initiatedH-ARQ process. When the Node-B 104 fails to decode the data sent by theWTRU 102, the Node-B 104 transmits a NACK message to the WTRU 102 viathe DL signaling channel 110 or does not transmit feedback which isinterpreted as a NACK by the WTRU 102. When the Node-B 104 succeeds todecode the data sent by the WTRU 102, the Node-B 104 transmits an ACKmessage to the WTRU 102 which releases the H-ARQ process for othertransmissions. The H-ARQ processes may either be designed to implementCC or IR. The RNC 106 controls overall operation of data transfers thatoccur between the Node-B 104 and the WTRU 102, including radio resourcesallocation. The WTRU 102 includes a data buffer 112 for storing E-DCHdata, an optional data lifespan timer 114 used to determine whether itis necessary to discard expired data, and a retransmission counter 116used to determine whether data transmitted by the WTRU 102 but notreceived by the Node-B 104 should be retransmitted or whether H-ARQtransmission should be terminated or optionally restarted. The buffer112, the lifespan timer 114 and the retransmission counter 116 arecontrolled by a controller 118. The controller 118 sets, (i.e., keepstrack of), the status of each transmission associated with an H-ARQprocess.

FIG. 2 is a flow diagram of a process 200 including method steps forcontrolling an H-ARQ process in accordance with the present invention.The H-ARQ process may be either synchronous or asynchronous. In asynchronous H-ARQ operation, the WTRU 102 keeps track of when responsesto data transmissions between the WTRU 102 and the Node-B 104 areexpected, and the periodicity of H-ARQ retransmissions is predetermined.In an asynchronous H-ARQ operation, the WTRU 102 transmits data andwaits for the feedback for a predetermined period of time.

After the WTRU 102 initiates the H-ARQ process and the retransmissioncounter 116, the WTRU 102 transmits data to the Node-B 104 via the E-DCH108 during a current TTI (step 202). In step 204, the WTRU 102 waits forfeedback from the Node-B 104. If the WTRU 102 receives an ACK messagefrom the Node-B 104, the WTRU 102 then sets the transmission status to“successful transmission”, releases the H-ARQ process and reinitiatesthe retransmission counter 116 (step 208) for subsequent datatransmissions.

If, at step 206, the WTRU 102 receives a NACK message or did not receiveany response, the WTRU 102 determines whether the retransmission countindicated by the retransmission counter 116 is less than or equal to themaximum number of allowed retransmissions (step 212).

If the retransmission count as determined at step 212 is less than themaximum number of allowed retransmissions, the WTRU 102 sets, ormaintains, the transmission status to “retransmission” and incrementsthe retransmission counter 116 (step 214). The retransmission counter116 is incremented each time the same data is retransmitted by the WTRU102.

If the retransmission count as determined at step 212 is equal to orgreater than the maximum number of allowed retransmissions, the H-ARQprocess transmission is terminated and reset for supporting subsequentdata transmissions (step 213). Optionally the WTRU 102 may set thetransmission status to “restarted transmission” and reinitiates theretransmission counter (step 216). After setting the transmission statusto “restarted transmission”, the WTRU 102 reinitiates the H-ARQtransmission process as a “new transmission” or the WTRU 102 mayoptionally release the H-ARQ process (step 218).

FIG. 3 is a flow diagram of a process 300 including method steps forimplementing CC in accordance with the present invention. The process300 is performed on a TTI basis (step 302). In step 304, the WTRU 102determines whether EU physical resources have been assigned by theNode-B 104 and whether an H-ARQ process is available for the WTRU 102 totransmit data to the Node-B 104 via the E-DCH 108. If EU physicalresources have not been assigned, the WTRU 102 waits for the allocationof EU physical resources and the transmission of data is delayed untilthe next TTI (step 302). If EU physical resources have been allocatedand an H-ARQ process is available, the WTRU 102 determines whether thedata is new data (step 306). If the data is determined to be new data instep 306, the WTRU 102 selects the highest priority data to transmit(step 308). Additionally, the WTRU 102 selects the MCS and TBS size thatmaximizes transmission of the highest priority data within an allowedlimit (step 310). TBS size is chosen based on the Node-B 104 signaledmaximum MCS and TBS size, transmit power available for the E-DCH 108,MCS, and the data available in the buffer 112 for transmission.

For each transport channel (TrCH), dedicated channel medium accesscontrol (MAC-d) flow or logical channel, a list of allowed TBS sizes, aretransmission limit and allowed transmission latency, (i.e., MAC data“lifespan”), are determined. The allowable MCS and TBS sizes are themaximum that the WTRU 102 is allowed to transmit for the currentphysical resources allocation period. The configuration is eithersignaled from the RNC 106 in accordance with radio resource control(RRC) procedures or uniquely specified by a standard. The chosen MCS andTBS size may be either explicitly signaled (preferably from the Node-B)or derived from an associated parameter such as a channel qualityindicator (CQI) and/or transport format combination (TFC) index. The CQImay represent the maximum allowed WTRU interference or transmit power.The Node-B 104 may signal this information in the initial channelassignment. Alternatively, the Node-B 104 may send this information whenthe WTRU 102 requests additional EU channel allocations.

In step 312, the WTRU 102 then generates at least one EU MAC (MAC-e)protocol data unit (PDU) based on the selected TBS size, and assigns anH-ARQ process for transmission of the MAC-e PDU. In step 314, the WTRU102 initializes the retransmission counter 116, increments an NDI andoptionally sets the lifespan timer 114 in the WTRU 102. The NDI is usedto indicate when new data is being transmitted and when the Node-B 104needs to clear the soft buffer associated with the H-ARQ process that isbeing transmitted. The initial value of the retransmission counter 116may be interpreted as a transmission of new data and, in such a case,the NDI parameter is not needed. The WTRU 102 then initiates an EUtransmission to the Node-B 104 identifying the current H-ARQ process,TBS size, (if not assigned by the Node-B 104), and MCS. The H-ARQprocess and MCS may be implicitly known by the Node-B 104 due to aspecified H-ARQ process operation, and thus may not need to be signaledby the WTRU 102 to the Node-B 104.

When CC is supported, the TBS size information is identified to theNode-B 104 for each transmission and retransmission, unless TBS isidentified by the Node-B 104 in the physical channel allocation.Retransmissions have the same MCS and TBS as applied in the initialtransmission in the case of CC.

Referring back to step 306, if it is determined that the data is not newdata, a determination is made as to whether the WTRU 102 utilizes thelifespan timer 114 (step 315). If the WTRU 102 utilizes the lifespantimer 114, the process 300 proceeds to step 316 to determine whether thelifespan timer 114 has expired. If the lifespan timer 114 has expired,the WTRU 102 discards the data and releases, (i.e., frees), the H-ARQprocess (step 318), and the process 300 returns to step 302. Optionally,when the lifespan timer 114 is close to expiration, the WTRU 102 may usea more robust MCS to increase the probability of successfultransmission.

The retransmission counter 116 in the WTRU 102 is incremented each timea data transmission is not successful and thus not acknowledged by theNode-B 104. If the lifespan timer 114 has not yet expired, or if theWTRU 102 does not utilize the lifespan timer 114, the process 300proceeds to step 320 for retransmission of the data whereby the WTRU 102determines whether the retransmission count is less than the maximumnumber of allowed retransmissions. If the retransmission count is lessthan the maximum number of allowed retransmissions, the status oftransmission is set to or maintained as “retransmission,” the WTRU 102increments the retransmission counter 116 (step 322) and uses the sameH-ARQ process, TBS, MCS and NDI, (if not incorporated with theretransmission counter) (step 324). The WTRU 102 then initiates an EUtransmission to the Node-B 104 identifying the H-ARQ process, (this maybe implicitly known and may not need be signaled to the Node-B), TBSsize (if not assigned by the Node-B), and MCS in the associated physicalcontrol channel (step 330).

If the retransmission count reaches or exceeds the maximum number ofallowed retransmissions, the process 300 proceeds to step 318 to discardthe data and release the H-ARQ process. Alternatively, if restartedtransmissions are determined to be allowed in optional step 325, thestatus of transmission is set to “restarted transmission,” and the WTRU102 initializes the retransmission counter 116, increments the NDI andassigns a new H-ARQ process (step 326). If the previously transmitteddata stored in the soft combining buffer is disrupting successiveretransmissions, it is better to clear the soft buffer and restart theH-ARQ transmission to increase the probability of successfultransmission. Therefore, when the maximum number of retransmissions fora particular H-ARQ process is reached, the NDI, (or an initializedretransmission count), is sent to indicate that the H-ARQ transmissionshave been restarted. When the Node-B 104 receives the incremented NDI,(or the transmission count set to the initial value), the Node-B 104clears the soft combining buffer of the previously received data.

In step 328, a new H-ARQ transmission is initiated using the same TBSand, optionally, a more robust MCS may be selected for the “newtransmission” to increase the probability of successful delivery (step328). In order to allow this change in MCS, the TBS may be segmentedinto several independent transmissions. In the case a transmission isbeing reinitiated with more redundancy (either by change of MCS or justless puncturing) the previous TBS may no longer fit in the allocatedphysical resource. In this case the original transmission may besegmented into multiple separate transmissions that do not exceed therequirement. The WTRU 102 then initiates an EU transmission to theNode-B which identifies the current H-ARQ process, (may be implicitlyknown to the Node-B), TBS size and MCS, (if not assigned by the Node-B),in the associated physical control channel (step 330).

FIG. 4 is a flow diagram of a process 400 including method steps forimplementing IR in accordance with the present invention. The process400 is performed on a TTI basis (step 402). In step 404, the WTRU 102determines whether EU physical resources have been assigned by theNode-B 104 and whether an H-ARQ process is available for the WTRU 102 totransmit data to the Node-B 104 via the E-DCH 108 (step 404). If EUphysical resources have not been assigned, the WTRU 102 waits for theallocation of EU physical resources and the transmission of data isdelayed until the next TTI (step 402). If EU physical resources havebeen allocated and an H-ARQ process is available, the WTRU 102determines whether the data is new data (step 406). If the data isdetermined to be new data in step 406, the WTRU 102 selects the highestpriority data to transmit (step 408). Additionally, the WTRU 102 selectsthe maximum TBS size and corresponding TFC maximizing transmission ofthe highest priority data using the most robust MCS allowed (step 410).

In step 412, the WTRU 102 then generates at least one MAC-e PDU based onthe selected TBS size, and assigns an H-ARQ process for transmission ofthe MAC-e PDU. In step 414, the WTRU 102 initializes the retransmissioncounter 116, increments an NDI and optionally sets the lifespan timer114 in the WTRU 102 (step 414). The NDI is used to indicate when newdata is being transmitted and when the Node-B 104 needs to clear thesoft buffer associated with the H-ARQ process that is being transmitted.The initial value of the retransmission counter 116 may be interpretedas a transmission of new data and, in such a case, the NDI parameter isnot needed. The WTRU 102 then initiates EU transmission to the Node-B104 identifying the current H-ARQ process, TBS size and MCS in theassociated physical control channel (step 430). The H-ARQ process andMCS may be implicitly known by the Node-B 104 due to a specified H-ARQprocess operation, and thus may not need to be signaled by the WTRU 102to the Node-B 104.

Referring back to step 406, if it is determined that the data is not newdata, a determination is made as to whether the WTRU 102 utilizes thelifespan timer 114 (step 415). If the WTRU 102 utilizes the lifespantimer 114, the process 400 proceeds to step 416 to determine whether thelifespan timer 114 has expired. If the lifespan timer 114 has expired,the WTRU 102 discards the data and releases, (i.e., frees), the H-ARQprocess (step 418), and the process 400 returns to step 402. Optionally,when the lifespan timer 114 is close to expiration, the WTRU 102 may usea more robust MCS to increase the probability of successfultransmission.

The retransmission counter 116 in the WTRU 102 is incremented each timea data transmission is not successful and thus not acknowledged by theNode-B 104. If the lifespan timer 114 has not yet expired, or if theWTRU 102 does not utilize the lifespan timer 114, the process 400proceeds to step 420 for retransmission of the data whereby the WTRU 102determines whether the retransmission count is less than the maximumnumber of allowed retransmissions. If the retransmission count is lessthan the maximum number of allowed retransmissions, the status oftransmission is set to or maintained as “retransmission,” and the WTRU102 increments the retransmission counter 116 and selects a more robustMCS, if allowed (step 422). In step 424, the WTRU 102 uses the sameH-ARQ process, TBS/TFC and NDI.

For IR, determination of the MCS and TBS size takes into account supportof the most robust MCS, what is required by the data which is ready totransmit in the WTRU 102, and available WTRU transmit power. With eachretransmission, a more robust MCS may be chosen for the same TBS. Theinitial transmissions with less robust MCS allow for a larger TBS size,but this size is restricted so that the same TBS can still be supportedby the most robust MCS. Also, for determination of the TBS, the WTRUavailable transmit power for EU must be taken into account the mostrobust MCS allowed, even though the most robust MCS may not be requiredfor successful transmission.

If the retransmission count reaches or exceeds the maximum, the process400 proceeds to step 418 to discard the data and release the H-ARQprocess. Alternatively, if restarted transmissions are determined to beallowed in step 425, the status of transmission is set to “restartedtransmission,” and the WTRU 102 initializes the retransmission counter116, increments the NDI and assigns a new H-ARQ process (step 426). Instep 428, the same TBS/TFC is used and an MCS is selected.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention.

While the present invention has been described in terms of the preferredembodiment, other variations which are within the scope of the inventionas outlined in the claims below will be apparent to those skilled in theart.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: at least one circuit configured to select a transport blocksize for transmission of enhanced uplink data; wherein the at least onecircuit is further configured to segment a medium access control (MAC)protocol data unit (PDU) into a plurality of segments on a conditionthat the MAC PDU does not fit in a transport block according to theselected transport block size; wherein the at least one circuit isfurther configured to produce a transport block having the transportblock size and include at least one of the plurality of segments; andwherein the at least one circuit is further configured to transmit thetransport block over an enhanced uplink channel and to transmit anindication of the transport block size over an associated physicalcontrol channel.
 2. The WTRU of claim 1 wherein the at least one circuitis further configured to transmit the transport block using one of aplurality of synchronous hybrid automatic repeat request (HARQ)processes.
 3. The WTRU of claim 1 wherein the at least one circuit isfurther configured to receive radio resource control (RRC) configurationinformation from a wireless network, wherein the RRC configurationinformation indicates a limit of a number of hybrid automatic repeatrequest (HARQ) transmissions for each medium access control fordedicated channel (MAC-d) flow.
 4. The WTRU of claim 1 wherein the atleast one circuit is configured to receive configuration informationfrom a radio network, wherein the configuration information indicatesallowable transport block sizes for the WTRU.
 5. The WTRU of claim 4,wherein the transport block size is selected based on the configurationinformation that indicates allowable transport block sizes.
 6. A methodfor transmitting enhanced uplink data, implemented by a wirelesstransmit/receive unit (WTRU), the method comprising: selecting atransport block size for transmission of enhanced uplink data;segmenting a medium access control (MAC) protocol data unit (PDU) into aplurality of segments on a condition that the MAC PDU does not fit in atransport block according to the selected transport block size;producing a transport block having the transport block size andincluding at least one of the plurality of segments; and transmittingthe transport block over an enhanced uplink channel; and transmitting anindication of the transport block size over an associated physicalcontrol channel.
 7. The method of claim 6 wherein the transport block istransmitted using one of a plurality of synchronous hybrid automaticrepeat request (HARQ) processes.
 8. The method of claim 6 furthercomprising receiving radio resource control (RRC) configurationinformation from a wireless network, wherein the RRC configurationinformation indicates a limit of a number of hybrid automatic repeatrequest (HARQ) transmissions for each medium access control fordedicated channel (MAC-d) flow.
 9. The method of claim 6 furthercomprising receiving configuration information from a radio network,wherein the configuration information indicates allowable transportblock sizes for the WTRU.
 10. The method of claim 9, wherein thetransport block size is selected based on the configuration informationthat indicates allowable transport block sizes.